Habitat Use by and Preferences of Juvenile Atlantic Salmon in Two Newfoundland Rivers

We examined habitat use by juvenile Atlantic salmon Salmo salar in two Newfoundland rivers: One with riffle habitat, the most typical rearing habitat for this species; the other with extensive areas of deeper slow-flowing water and rooted macrophytes. We derived habitat-use curves for both habitat types from field data, then measured habitat availability to calculate habitat preference in each area. Both habitat use and habitat preference varied between young of the year and older juveniles (parr). There was little difference between habitat used by young of the year in the two rivers; however, parr habitat use differed significantly for some of the variables between sites. Water velocity at the fishˈs snout was the principal variable that defined habitat use. Substrate was unimportant in the riffle habitat but it had influence on habitat use in the slow-water environment. Water depth was unimportant within the range of depths examined during the present study. The use and preference curves for each variable were influenced by other habitat components, especially in the slow-water habitat. The differences noted between habitat preference measured in the two habitat types suggest that either the method used to compute preference is flawed or that other (unmeasured) factors are influencing habitat use. With our present understanding of the habitat requirements of juvenile Atlantic salmon, locally derived habitat-use information is recommended for habitat modeling.